Effects Of Controlled-Released Blend Bulk Fertilizers And Sowing Date On Photosynthetic Characteristics And Nitrogen Utilization Of Winter Wheat

In order to explore the effects of different blend ratios of normal urea and controlled-release urea on photosynthetic characteristics and nitrogen utilization of winter wheat under different sowing dates,two experiments were conducted in this study.The first experiment was arranged in the winter wheat season of 2016–2017.Five blend ratios were applied at 0:10?C?,3:7?UC1?,4:6?UC2?,5:5?UC3?and 10:0?U?.The second experiment was conducted in the wheat growing season of 2017-2018.Split plot design was adopted with three sowing dates as the main plot and three blend ratios as the sub-plot.Winter wheat was sown respectively at Oct10?October 10?,Oct20?October 20?,Oct30?October 30?with nitrogen application of UC1,UC2 and UC3.The effects of different blend ratios and sowing dates on yield,photosynthetic characterics of flag leaf after anthesis,nitrogen utilization of plants,and soil total nitrogen were studied.The main results were as follows:1 Effects of blend ratio and sowing date on the yield of winter wheatThe yield of controlled-released blend bulk fertilizer was significantly higher than that of pure controlled-release urea?C?and pure normal urea?U?.Higher normal urea ratio of blend bulk fertilizer enhanced higher yield.The effects of blend ratios on spike number were same as yield,and UC3 had highest spike number among all treatments.The 1000-grain weight increased with the increase of controlled-release urea ratio.The yield at different sowing dates were Oct20,Oct10>Oct30.There was no significant difference between Oct 20 and Oct 10treatments.With the delay of sowing date,spike number per hectare significantly decreased,grain number per spike and 1000-grain weight significantly increased.Spike number of sowing at Oct 10 and Oct 20 showed UC3>UC2>UC1,and sowing at Oct 30 showed UC1?UC2>UC3.2 Effects of blend ratio and sowing date on photosynthetic characteristic of flag leaf after anthesisThe nitrogen content of flag leaf could maintain the green leaf area and SPAD value at a high level after anthesis with the increase of controlled-release urea ratio and the delay of sowing date.Thus it effectively delayed leaf senescence and significantly increased net photosynthetic rate and product.Meanwhile,the light capture performance,the light energy transformation into electric energy,transfer efficiency of electrons in electron transfer chain,and the electron donor side and the acceptor side of photosystem II was improved significantly.The PI_ABS of pure controlled-release urea?C?treatment was 29.6%higher than that of normal urea treatment,and Oct30 was 12.2%and 56.3%higher than Oct20 and Oct10,respectively.Photosynthetic nitrogen use efficiency?PNUE?was negatively correlated with specific leaf nitrogen.High controlled-release urea ratio treatment significantly increased photosynthetic nitrogen use efficiency.With the delay of sowing date,specific leaf nitrogen increased significantly with decreasing of PNUE.Photosynthetic characteristics of pure controlled-release urea treatment?C?was better than other treatmeans in the first experiment,and Oct30 UC1 was best in the second experiment.3 Effects of blend ratio and sowing date on nitrogen absorption and utilization of winter wheatThe high proportion of normal urea treatment significantly increased soil total nitrogen content,per-anthesis nitrogen translocation amount and contribution rate of translocated to grain.The high proportion of controlled-release urea treatment significantly increased soil total nitrogen content and nitrogen accumulation amount during flowering to maturity stage,the same as its contribution rate to grain.With the postponement of sowing date,the soil total nitrogen content in the whole period,nitrogen accumulation amount and its contribution rate after anthesis increased;on the contrary,nitrogen translocation amount and rate and its contribution rate to grain decreased.Blend bulk fertilizer significantly increased nitrogen agronomic efficiency,partial productivity of nitrogen and nitrogen apparent recovery.In addition,nitrogen use efficiency increased significantly with the increase of normal urea proportion.With the delay of sowing date,nitrogen use efficiency showed a downward trend.The results of the two-year experiments showed that the nitrogen use efficiency with the blend ratio of UC3 was highest.The second experiment showed that sowing date delayed for10 days,which could further improve the nitrogen use efficiency.Combined with the two-year experimental results,high controlled-release urea ratio and the delay of sowing date had a positive effect on the photosynthetic characteristics of flag leaves after anthesis at a higher level.The treatment of 5:5 blend ratio with sowing on October 10 had the highest yield and nitrogen use efficiency.Yield and nitrogen use efficiency were further improved by 10 days?October 20?after normal sowing date.Under the condition of sowing on October 20,the optimum mixing ratio was 5:5.